doc/mgr: document ceph-exporter

Add stub-level information for the documentation of ceph-exporter. Explicit configuration instructions are still missing from this documentation, and should in the future be supplied.

Signed-off-by: Zac Dover <zac.dover@clyso.com>

diff --git a/doc/mgr/prometheus.rst b/doc/mgr/prometheus.rst
index 8f69e465eb671a8705e5a6db62a3b7d5ba092af1..d19de71a08ffda472f8d9215fe9c7a82eddafc5a 100644 (file)
--- a/doc/mgr/prometheus.rst
+++ b/doc/mgr/prometheus.rst
@@ -24,6 +24,19 @@ Enable the ``prometheus`` module by running the below command :
 
    ceph mgr module enable prometheus
 
+ceph-exporter
+=============
+
+``ceph-exporter`` works alongside the Prometheus manager module. The two
+components have distinct responsibilities:
+
+- The **Prometheus manager module** exposes all cluster-level metrics by
+  default other than Ceph daemon performance counters. However, these metrics
+  may be exported by the Prometheus manager module by setting the module option
+  :confval:`mgr/prometheus/exclude_perf_counter` to `false`.
+- The **ceph-exporter daemon** exposes only Ceph daemon performance counters
+  as Prometheus metrics, running on each host in the cluster.
+
 Configuration
 -------------